The moth borer Diatraea tabernella Dyar (Lepidoptera: Crambidae) feeds on sugarcane causing holes and tunnels in the stalks resulting in yield losses. Damage facilitates the entry of red rot (Colletotrichum falcatum) causing inversion of sucrose in the sugarcane juice. Two types of damage that can be related to sugar loss were assessed and analyzed: the percentage of internodes bored in the stalk and the internal damage (=length of borer tunnels). After a preliminary assessment on borer damage in 2012, a new study was conducted in 2016 to thoroughly investigate the impact of D. tabernella not only on cane and sugar yield, but also on stalk parameters (length, diameter, stalk mass, etc.). This assessment was conducted on eight varieties and was carried out on three samples (replicates) of five stalks per variety grouped in five damage levels (0, 1, 2, 3 and 4 internodes bored). The results indicated that stalk mass, fiber and sugar yield were significantly affected by the stalk borer. Sugar yield decreased up to 2.56 t of sugar per hectare, with damage level 3 similar to the yield with no damage (level 0). Internodes of cultivars E07-09, Na56-42, SP01-2050 and SP81-3250 were less damaged at the two-internode category and had lower sugar losses. There was an exact linear relationship negative (decreasing) between sugar yield (t/ha) and damage levels (y = −0.579x + 9.324, R 2 = 0.9069) with a range from 12.9% with damage level 1 to 26.47% loss with damage level 4.